The present invention relates to a switch apparatus used in the transmission of redundant audio and video signals, such as Cable TV (CTV) signals. More particularly, the present invention relates to a switch apparatus used in the transmission of redundant Cable TV (CTV) signals including symmetric and asymmetric redundant CTV signals.
In recent years, the cable television industry has grown tremendously, with the likelihood of continuing to grow in future years. Future growth could enable the cable television industry to provide hundreds, possibly thousands of cable television channels to consumers. As the cable television industry offers more and more channels, it has become increasingly important to maintain a higher level of signal quality and to minimize breakdowns in cable television systems in order to avoid loss of service to customers.
It is known that a failure in less, split channels is more readily detected than a failure in more, combined channels. Accordingly, a CTV signal is typically divided or split into multiple circuit paths to aid in maintaining a higher level of signal quality when carried on fiber-optic transmission lines.
Also, a secondary CTV signal is used as a backup in case the primary CTV signal fails in order to minimize breakdowns in the system. For economical reasons, the secondary CTV signal is not divided or split since it is rarely used in the transmission of the CTV signal to the end user. The primary CTV signal is divided or split into multiple parts or circuit paths.
The division or splitting of the CTV signal may be asymmetric, where one part may contain more channels than another part. To avoid the asymmetric effects caused by the division or splitting at the receiving end, a typical practice in the CTV environment is to immediately combine the split CTV signals at the earliest convenient point after they are received. However, if there is a failure in the transmission of the signals, for example a cable cut, an optic-electric converter malfunction, or a bad electrical connection, etc., it is difficult to monitor the changes from a combined signal to promptly detect a failure. As a result, switching from the primary signal path(s) to the secondary signal path may not be timely. The transmitted signals may be interrupted without backup. The repair service may be delayed to correct the problem. Such interruptions or delays are expensive to the cable television industry and result in customer frustration and dissatisfaction.
Accordingly, there is a need for a switch apparatus to adapt to a secondary backup path to minimize signal breakdowns. Also, there is a need for such a switch apparatus to accommodate split-linked primary signal paths to maintain a higher level of signal quality and to readily detect a failure. Further, there is a need for such a switch apparatus to be immune from the asymmetry effects caused in the division or splitting of a redundant signal, e.g. a redundant CTV signal.
The present invention provides a solution to these and other problems and offers advantages over the prior art.
The present invention relates to a switch apparatus used in the transmission of redundant audio and video signals, such as Cable TV (CTV) signals. More particularly, the present invention relates to a switch apparatus used in the transmission of redundant Cable TV (CTV) signals including symmetric and asymmetric redundant CTV signals.
The present invention provides a switch apparatus which interconnects a redundant CTV signal. A redundant CTV signal can be defined as having a primary CTV signal and a secondary CTV signal. The present invention also provides a switch apparatus which interconnects a symmetric redundant CTV signal and an asymmetric-redundant CTV signal. A symmetric redundant CTV signal can be defined as a signal which is divided or split into multiple signal paths or channel paths, where each path contains the same amount of channels. An asymmetric redundant CTV signal can be defined as a signal which is divided or split into multiple signal paths or channel paths, where one path may contain more channels than another part.
In a normal operation, the switch apparatus is operated in a first position. Each of the primary signal paths is monitored such that when there is a failure in any one of the primary signal paths, the switch apparatus is switched to a second position. The secondary channels are then connected and outputted to the end user. When the failed primary signal path is returned, the switch apparatus is switched back to the first position. The primary signal paths are combined, and the combined signals are outputted to the end user. A timer may be used to provide a delay for the switching back in case that the recovery from the failure is temporary.
In one embodiment of the present invention, the primary channels are divided or split into two signal paths, and the secondary channels are not divided or split and include the same channels as the combination of all primary channels. The switch apparatus which is adapted to the split primary channels and the non-split secondary channels has the advantages of minimizing breakdowns, maintaining a higher level of signal quality when the CTV signal is carried on fiber-optic transmission lines, and readily monitoring for failures. Many other advantages of the present invention are also provided. For example, the switch apparatus of the present invention is immune to the asymmetric effects caused in the splitting of the primary channels, where one part contains more channels than the other part.
In one embodiment of the present invention, a switch apparatus comprises: a first input port including a first switch for switching between a first position to input a first set of primary channels and a second position to connect to a termination; a second input port including a second switch for switching between a first position to input a second set of primary channels and a second position to input a set of secondary channels, the set of secondary channels including the sum of the first and second sets of primary channels; a controller for controlling the first switch and the second switch, wherein when the controller detects a predetermined condition, the controller switches the first and second switches simultaneously from the first positions to the second positions, and when the controller detects that the predetermined condition is over, the controller switches the first and second switches simultaneously from the second positions to the first positions; and an output port including a combiner for outputting combined first and second sets of primary channels when the first and second switches are switched to the first positions, and for outputting the set of secondary channels when the first and second switches are switched to the second positions.
According to one aspect of the present invention, the controller includes a first monitor for monitoring a condition of the first set of primary channels proximate at the first input port; and a second monitor for monitoring a condition of the second set of primary channels proximate at the second input port. When the condition in either of the first and second sets of primary channels reaches the predetermined condition, the controller switches the first and second switches from the first positions to the second positions.
Another aspect of the present invention is that the controller includes a timer. When the predetermined condition is over, the controller switches the first and second switches from the second positions to the first positions after a period defined by the timer.
A further aspect of the present invention is that the first set of channels includes more or less channels than the second set of channels. Alternatively, the first set of channels includes the same number of channels as the second set of channels.
The present invention also provides a cable system for transmitting primary channels which are split into at least two sets and secondary channels from a head-end of a receiver to an end user. The cable system comprises: the head-end for receiving signals, and cables for transmitting the primary channels and the secondary channels to a hub. The hub comprises a switch apparatus including: a first input port including a first switch for switching between a first position to input the first set of primary channels and a second position to connect to a termination; a second input port including a second switch for switching between a first position to input the second set of primary channels and a second position to input the secondary channels; a controller for controlling the first switch and the second switch, wherein when the controller detects a predetermined condition, the controller switches the first and second switches simultaneously from the first positions to the second positions, and when the controller detects that the predetermined condition is over, the controller switches the first and second switches simultaneously from the second positions to the first positions; and an output port including a combiner for outputting combined first and second sets of primary channels when the first and second switches are switched to the first positions, and for outputting the set of secondary channels when the first and second switches are switched to the second positions.
The present invention also provides a method of switching between primary channels and secondary channels in a receiver of a cable system, the primary channels being split into two sets, comprising: connecting a first switch to a first position and a second switch to a first position; monitoring the first set of primary channels and the second set of primary channels: a) if either-of the first and second sets of the primary channels is in a predetermined condition: 1) switching the first switch to a second position and the second switch to a second position simultaneously; and 2) outputting the secondary channels; b) if neither of the first and second sets of the primary channels is in the predetermined condition: 1) combining the first and second sets of the primary channels; and 2) outputting the combined primary channels.
One aspect of the present invention is that the method further comprises switching from the second positions of the first and second switches to the first positions when the predetermined condition is over. The switching from the second positions to the first positions when the predetermined condition is over may be delayed for a period of time.
Another aspect of the present invention is that the splitting of the primary channels is asymmetric such that the first set of the primary channels has more or less channels than the second set of the primary channels.
Accordingly, the present invention minimizes signal breakdowns, accommodates split-linked primary signal paths to maintain a higher level of signal quality and readily detects a failure, and is immune from the asymmetry effects caused in the division or splitting of a redundant signal.